1 is Corydalis lutea.
2 is a Helianthus but that's not a Genus I know so I can't provide the species.
3. is a Hypericum possibly H perforatum but I can't see the leaves closely enough to tell for certain.

could nr.2 be Heliopsis helianthoides?

Number 2 was sent to me as Helianthus mollis a couple years ago, but the person who sent it sent me a lot of things that were incorrectly labeled so I'm just trying to get my names straight.

Floral is probably right on the 3rd photo. The two species that are similar (H. punctatum and H. pseudomaculatum) usually have black spots that are evident on the petals. Yours seem pretty clear. And I also thought that linaria was right - That sunflower-type plant is definitely not Helianthus mollis, because those have densely hairy stems. It looks a lot like our Ox-eye Sunflower (Arkansas species Heliopsis helianthoides var. scabra). However, those have rough stems. So I checked USDA and you get H. helianthoides var. helianthoides, which is mostly smooth.

I don't know Heliopsis so my Helianthemum id is probably suspect.